Chemically amplified positive photosensitive resin composition

ABSTRACT

A photosensitive resin composition suitable for forming a thick film and an ultra-thick film used for forming a thick resist pattern used in the process of forming a magnetic pole on a magnetic head and a bump, which comprises (A) an alkali soluble novolak resin, (B) an alkali soluble acrylic resin, (C) an acetal compound, and (D) an acid generator. A polycondensate comprising a structural unit represented by the following general formula (I) (wherein R represents a saturated alkyl group having 1 to 20 carbon atoms, n is an integer of 1 to 10) as an acetal compound

TECHNICAL FIELD

The present invention relates to a positive-working photosensitive resincomposition, more specifically to a chemically amplifiedpositive-working photosensitive resin composition suitable for forming athick film and an ultra-thick film appropriately used in producing asemiconductor device, a flat panel display (FPD), a circuit board, and amagnetic head, in particular, in forming the magnetic pole of a magnetichead and the protuberance electrode called “bump” for use as aconnecting terminal in a large-scale integrated circuit (LSI).

BACKGROUND ART

Conventionally, photolithographic technology has been used in formingmicroelements or carrying out a fine processing in a variety of fields,for example, in production of semiconductor integrated circuits such asLSIs, display screens of FDPs, circuit boards for thermal heads, andothers. Positive- or negative-working photosensitive resin compositionshave been used for forming resist patterns in the photolithographictechnology. Among these photosensitive resin compositions,positive-working photosensitive resin compositions containing an alkalisoluble resin together with a quinonediazide compound as aphotosensitive agent have been used widely. Various kind of suchcompositions were described as “novolak resin/quinonediazide compounds”in a large number of literatures, for example, including Japanese PatentApplication Publication (JP-B) Nos. 54-23570 and 56-30850 and JapanesePatent Application Laid-Open (JP-A) Nos. 55-73045 and 61-205933.Research and developments on these compositions containing a novolakresin and a quinonediazide compound have been carried out from bothaspects of the novolak resins and photosensitive agents.

On the other hand, in the fields demanding a thick film processing suchas magnetic head and bump, it is necessary to form a resist patternhaving a high-aspect ratio and perpendicular wall. However, theconventional photoresists described above have problems, for example, ofinsufficient resolution or sensitivity, inability to produce desirableresist patterns, and the like, because of deterioration in lighttransmission of the films associated with increase in thickness; andthus there exists a need for a new photoresist that can overcome theproblems.

As dry-film-system photosensitive resin compositions that can form athick resist pattern, there have been hitherto known a photosensitiveresin composition comprising a novolak resin, an acetal compound havingrepeating acetal units in the main chain wherein each a-carbon atom ofthe alcohol component of the acetal units is aliphatic, and an acidgenerator (JP-A No. 53-133429); a photosensitive resin compositioncomprising an alkali soluble resin such as novolak resin, an acetalcompound, an acid generator, and additionally a particular additive suchas an alkyl acrylate (JP-A No. 57-37349); and a photosensitive resincomposition comprising an alkali soluble resin such as novolak resin, anacetal compound, and an acid generator (JP-A No. 58-114031). Further, asthe photosensitive resin compositions comprising an acetal compound andan acid generator, known are a photosensitive resin compositioncomprising a novolak resin prepared using three different phenols, anacetal compound, and an acid generator (JP-A No. 62-124556); aphotosensitive composition comprising a novolak resin having an acetalbond in the molecule and an acid generator (JP-A No. 62-215947); and aphotoresist comprising a novolak resin, an acetal compound(chlorobenzaldehyde-diphenoxyethylacetal), and an acid generator(2-alkoxyphenyl-4,6-bis(trichloromethyl)-s-triazine) (JP-A No.4-182650). Furthermore, there are indicated a photosensitive resincomposition comprising a polymer having an acid-dissociative functionalgroup, a polyvinyl lower alkyl ether, and an acid generator (JP-A No.2001-281863) as the photosensitive resin composition for forming anultra-thick film resist having a thickness of 20 μm or more that aresuitable for forming a bump; and a photosensitive resin compositioncomprising an acid generator and an alkali soluble novolak resin ofwhich a part of the hydrogen atoms of the phenolic hydroxyl groups aresubstituted with a 1,2-naphthoquinone-diazido-sulfonyl group (JP-A No.2001-312060) as the photosensitive resin composition compatible with thethick resists having a thickness of 3 μm or more that are suitable forproducing a magnetic head. However, for making the composition morecompatible with an ultra-thick film, for example, having a thickness of20 to 100 μm, there exist needs currently, for example, for improvementof the resolution thereof for production of minute rectangular patternshaving a high aspect ratio, good pattern reproducibility, improvement ofthe heat resistance of the pattern obtained, and improvement of thethroughput (yield per unit time) during production for reduction inproduction cost, thus demanding further improvement of thephotosensitive resin composition currently.

Under the circumstances described above, an object of the presentinvention is to provide a chemically amplified positive-workingphotosensitive resin composition compatible with a thick film processingand an ultra-thick film processing that has high sensitivity and highfilm retention ratio (after development), excellent in coatingproperties, capable of forming favorable high-resolution patterns, andalso excellent in the heat resistance of the patterns obtained.

Another object of the present invention is to provide a chemicallyamplified positive-working photosensitive resin composition for use inthe electrolytic gold-, copper-, nickel- or solder-plating step of thesemiconductor packaging technology.

DISCLOSURE OF THE INVENTION

As a result of intensive investigations to solve the problems, theinventors have found that the object of the present invention could beachieved by using a particular chemically amplified positive-workingphotosensitive resin composition comprising an alkali soluble novolakresin, an acetal compound, and a compound generating an acid byirradiating with radiation (acid generator) as that for use in theprocesses, for example, using a thick film having a thickness of morethan 5 μm and an ultra-thick film having a thickness of more than 20 μmand completed the present invention.

Accordingly, the present invention relates to a chemically amplifiedpositive-working photosensitive resin composition comprising (A) analkali soluble novolak resin, (B) an alkali soluble acrylic resin, (C)and acetal compound, and (D) an acid generator.

DETAILED EXPLANATION OF THE INVENTION

Hereinafter, the present invention will be described in more detail.

The alkali soluble novolak resin (A) for use in the chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention is not particularly limited if it is an alkali solublenovolak resin used in hitherto publicly known photosensitive resincompositions containing an alkali soluble resin and a photosensitiveagent having a quinonediazide group. The novolak resins favorably usedin the present invention can be prepared by polycondensation of a singlespecies of phenol or a mixture of the plural species of phenols with analdehyde or aldehydes such as formalin.

Examples of the phenols constituting the novolak resins include phenol,p-cresol, m-cresol, o-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol,2,5-dimethylphenol, 2,6-dimethylphenol, 3,4-dimethylphenol,3,5-dimethylphenol, 2,3,4-trimethylphenol, 2,3,5-trimethylphenol,3,4,5-trimethylphenol, 2,4,5-trimethylphenol, methylene bisphenol,methylene bis-p-cresol, resorcin, catechol, 2-methylresorcin,4-methylresorcin, o-chlorophenol, m-chlorophenol, p-chlorophenol,2,3-dichlorophenol, m-methoxyphenol, p-methoxyphenol, p-butoxyphenol,o-ethylphenol, m-ethylphenol, p-ethylphenol, 2,3-diethylphenol,2,5-diethylphenol, p-isopropylphenol, a-naphthol, β-naphthol, and thelike; and these phenols may be used singly or as a mixture of pluralspecies. Among these phenols, the combined use of two or more phenolcompounds, for example m-cresol and p-cresol, often leads to morepreferred results.

Examples of the aldehydes include paraformaldehyde, acetaldehyde,benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde, and the like aswell as formalin; and these aldehydes may also be used singly or as amixture of plural species.

The weight average molecular weight of the alkali soluble novolak resinfor use in the chemically amplified positive-working photosensitiveresin composition according to the present invention is preferably from5,000 to 100,000 and more preferably from 5,000 to 50,000 as determinedby polystyrene standards.

In addition, examples of the alkali soluble acrylic resins (B) used inthe present invention include (B-1) alkali soluble polyacrylic esters,(B-2) alkali soluble polymethacrylic esters, and (B-3) alkali solublepoly(acrylic ester-methacrylic ester) containing at least one acrylicester and at least one methacrylic ester as the structural units. Theseacrylic resins may be used alone or in combination of two or more. Inthe present invention, the alkali soluble acrylic resin (B) is normallyused in an amount of from 2 to 200 parts, preferably from 10 to 50parts, by weight with respect to 100 parts by weight of alkali solublenovolak resin (A).

It is preferred that the acrylic resin contains as the monomer componentan organic acid monomer or an acrylic or methacrylic esters having ahydroxy group on its side chain as the copolymerization component tomake itself alkali soluble, but the copolymer components providing theresin with alkali solubility are not limited to an organic acid monomeror an acrylic or methacrylic ester having a hydroxy group on the sidechain.

Examples of the monomer components constituting these alkali solublepolyacrylic esters, polymethacrylic acid esters, and poly(acrylicester-methacrylic ester) include acrylic esters, methacrylic esters,organic acid monomers and other copolymerizable monomers. Among thesemonomer components constituting these polymers, favorable examples ofthe acrylic esters, methacrylic esters, and organic acid monomersinclude the followings:

Acrylic esters: methyl acrylate, ethyl acrylate, n-propyl acrylate,n-butyl acrylate, n-hexyl acrylate, isopropyl acrylate, isobutylacrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate,2-chloroethyl acrylate, methyl a-chloroacrylate, phenyl a-bromoacrylate,etc.

Methacrylic esters: methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, n-butyl methacrylate, n-hexyl methacrylate, isopropylmethacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexylmethacrylate, benzyl methacrylate, phenyl methacrylate, 1-phenylethylmethacrylate, 2-phenylethyl methacrylate, furfuryl methacrylate,diphenylmethyl methacrylate, pentachlorophenyl methacrylate, naphthylmethacrylate, isoboronyl methacrylate, benzyl methacrylate, hydroxyethylmethacrylate, hydroxy propyl methacrylate, etc.

Organic acid monomers: monocarboxylic acids such as acrylic acid,methacrylic acid, and crotonic acid; dicarboxylic acids such as itaconicacid, maleic acid, fumaric acid, citraconic acid, and mesaconic acid,and the anhydrides of these dicarboxylic acids; 2-acryloyl hydrogenphthalate, 2-acryloyloxypropyl hydrogen phthalate, etc.

Examples of other copolymerizable monomers include maleic diesters,fumaric diesters, styrene and styrene derivatives such as4-fluorostyrene, 2,5-difluorostyrene, 2,4-difluorostyrene,p-isopropylstyrene, o-chlorostyrene, 4-acetylstyrene, 4-benzoylstyrene,4-bromostyrene, 4-butoxycarbonylstyrene, 4-butoxymethylstyrene,4-butylstyrene, 4-ethylstyrene, 4-hexylstyrene, 4-methoxystyrene,4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene,2,4,5-trimethylstyrene, 4-phenylstyrene, and 4-propoxystyrene,acrylonitrile, (meta)acrylamide, vinyl acetate, vinyl chloride, andvinylidene chloride. Styrenes and styrene derivatives are preferable asthe other copolymerizable monomer. These other copolymerizable monomersmay be used as needed in an amount in the range that the resultingacrylic resin achieves the object of the invention.

Preferred examples of the alkali soluble acrylic resin for use in thechemically amplified positive-working photosensitive resin compositionaccording to the present invention include a copolymer containing astructural unit derived from (meth)acrylic acid and/or a structural unitderived from hydroxyalkyl methacrylate and a structural unit derivedfrom alkyl methacrylate, as well as a structural unit derived fromstyrene as needed; more preferably a copolymer containing a structuralunit derived from (meth)acrylic acid or hydroxyethyl methacrylate, astructural unit derived from methyl methacrylate, and a structural unitderived from n-butyl acrylate, as well as a structural unit derived fromstyrene as needed. Preferable range of the weight-average molecularweight of the acrylic resin as determined by polystyrene standardsaccording to the present invention is from 2,000 to 200,000 and morepreferably from 20,000 to 100,000.

The acetal compound (C) for use in the chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention is not particularly limited if it is one of acetalcompounds including those described in the aforementioned patentdocuments illustrated as prior art literatures or others, but preferablyan acetal compound having the structural unit represented by thefollowing general formula (I) in the molecule. The acetal compoundhaving the structural unit represented by general formula (I) in themolecule preferably has a weight-average molecular weight in the rangeof 100 to 100,000 and more preferably 200 to 5,000 as determined bypolystyrene standards.

In the formula (I) above, R represents an alkyl group having 1 to 20carbon atoms, preferably a saturated alkyl group having 3 to 10 carbonatoms. Typical examples of more preferable alkyl groups include anisopropyl group, a tert-butyl group, a 1-methylpropyl group, and a1-ethylpropyl group. In addition, n is an integer of 1 to 10, preferably2 to 4.

Typical examples of the acetal compounds represented by general formula(I) above are polycondensates having the repeating units represented bygeneral formula (I) above that are prepared by reacting an aldehyde:RCHO, a dialcohol: RCH(OH)₂, or an acetal: RCH(OR¹)₂ (in the formula, Rrepresents a group defined above and R¹ represents an alkyl group) withethylene glycol or polyethylene glycol represented by formula:

wherein n is the integer defined above.

In the present invention, the acetal compound (C) is normally used in anamount of from 5 to 50 parts by weight, preferably from 20 to 30 partsby weight, with respect to 100 parts by weight of the alkali solublenovolak resin (A).

The acid generator (D) for use in the chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention, i.e., the compound that generates an acid byirradiating with a radiation, is not particularly limited if itgenerates an acid by irradiating with a radiation.

Typical examples of these acid generators include compounds used as anacid generator in conventional chemically amplified resists. Such acidgenerators include onium salts such as iodonium salts, sulfonium salts,diazonium salts, ammonium salts, and pyridinium salts;halogen-containing compounds such as haloalkyl group-containinghydrocarbon compounds and haloalkyl group-containing heterocycliccompounds (halomethyltriazine derivatives, etc.); diazo ketone compoundssuch as 1,3-diketo-2-diazo compounds, diazobenzoquinone compounds, anddiazonaphthoquinone compounds; sulfone compounds such as β-ketosulfoneand β-sulfonylsulfone; sufonic acid compounds such as alkylsulfonicesters, haloalkylsulfonic esters, arylsulfonic esters, andiminosulfonates; and naphthalimide compounds such asN-(trifluoromethylsulfonyloxy)-1,8-naphthalimide,N-(p-toluenesulfonyloxy)-1,8-naphthalimide,N-(methylsulfonyloxy)-1,8-naphthalimide, andN-(camphorsulfonyloxy)-1,8-naphthalimide. These compounds may be usedsingly or as a mixture of two or more. The acid generator (D) isnormally used in an amount of from 0.05 to 10 parts by weight,preferably from 0.5 to 3.0 parts by weight with respect to 100 parts byweight of the alkali soluble novolak resin in the present invention.

Particularly preferable examples of the acid generators for use in thepresent invention include triazine-based acid generators represented by2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis-(trichloromethyl)-s-triazine,cyano-based acid generators represented by5-methylsulfonyloxyimino-5H-thiophen-2-ylidene-2-methylphenylacetonitrile,and imide-based acid generators represented byN-(trifluoromethylsulfonyloxy)-1,8-naphthalimide.

Examples of the solvents for use in dissolving the alkali solublenovolak resin, alkali soluble acrylic resin, acetal compound, and acidgenerator according to the present invention include ethylene glycolmonoalkylethers such as ethylene glycol monomethylether and ethyleneglycol monoethylether; ethylene glycol monoalkylether acetates such asethylene glycol monomethylether acetate and ethylene glycolmonoethylether acetate; propylene glycol monoalkylethers such aspropylene glycol monomethylether and propylene glycol monoethylether;propylene glycol monoalkylether acetates such as propylene glycolmonomethylether acetate and propylene glycol monoethylether acetate;lactic acid esters such as methyl lactate and ethyl lactate; aromatichydrocarbons such as toluene and xylene; ketones such asmethylethylketone, 2-heptanone, and cyclohaxanone; amides such asN,N-dimethylacetamide and N-methylpyrrolidone; and lactones such asγ-butylolactone. These solvents may be used singly or as a mixture oftwo or more solvents.

The photosensitive resin composition according to the present inventionmay further contain, as needed, other additives such as dyes, adhesiveaids and surfactants. Examples of the dyes include Methyl Violet,Crystal Violet, and Malachite Green. Examples of the adhesive aidsinclude alkylimidazolines, butyric acid, alkyl acids,polyhydroxystyrene, polyvinylmethylether, t-butylnovolak, epoxysilane,epoxy polymers, and silane. Examples of the surfactants include nonionicsurfactants including polyglycols and the derivatives thereof such aspolypropylene glycol, polyoxyethylene lauryl ether, fluorine-containingsurfactants such as Fluorad (trade name, manufactured by Sumitomo 3MCo., Ltd.), Magafac (trade name, manufactured by Dainippon Ink andChemicals, Inc.), Surflon (trade name, manufactured by Asahi GlassCompany, Ltd.), and organosiloxane surfactants such as KP341 (tradename, manufactured by Shin-Etsu Chemical Co., Ltd.).

Incidentally, bonding methods in the semiconductor packaging technologyinclude wire bonding method of connecting a chip to external circuits byusing wires, TAB (Tape Automated Bonding) method of connecting a chip toexternal circuits by using bumps (metal protuberance), and FC (FlipChip) method. The bump-forming technique is used both in the TAB and FCmethods, and the bumps are formed on the electrodes of the chip or theelectrodes on the substrate. These bumps are formed usually according tothe following procedure. That is, first a barrier metal foil as anelectrically conductive layer is laminated on a silicon wafer carryingLSI elements and then a photosensitive resin composition, so calledresist is applied thereon to form a photoresist film. Next thephotoresist film is exposed to light through a mask in such a mannerthat bump-forming areas become uncovered and developed to form apattern. An electrode material such as gold or copper is then depositedthereon by electrolytic plating by using the pattern as a template.After removal of the resist film remaining thereon, the barrier metal isremoved by etching. The wafer is then cut into square chips, which aresupplied to the step, for example, of the packaging by TAB or packagingby flip chip.

As described above, a patterned resist is produced by using aphotosensitive resin composition before the bump formation, thechemically amplified positive-working photosensitive resin compositionaccording to the present invention is favorably used as a resist in thebump-forming processes, for example, in the cyan or non-cyanelectrolytic gold plating steps in gold bump-forming process.Accordingly, the present invention relates to a chemically amplifiedpositive-working photosensitive resin composition used in the cyan ornon-cyan electrolytic gold plating steps in the gold bump-formingprocesses of the semiconductor packaging technology.

In addition, in production of LSI elements, FDPs such as LCD (liquidcrystal display) and circuit boards, not only bumps but also wiring andothers are formed by plating. In electrolytic plating for bumps andwiring, other metals such as copper, nickel, and solder are also used asplating materials as well as gold. The chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention can also be used preferably as a resist for use in thestep of plating with copper, nickel, solder, or the like in thebump-forming and wiring-forming plating steps. Accordingly, the presentinvention also relates to a chemically amplified positive-workingphotosensitive resin composition that is used in copper-, nickel-, orsolder-plating steps.

Further, not only a formation of a single plating layer, but alsocontinuous formations of multiple plating layers by use of the sameresist pattern have been widely conducted. The chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention is also characterized by being used in platingprocesses wherein the electrolytic gold plating and copper-, nickel-, orsolder-plating are carried out in continuous multilayer plating steps.The order of the gold-plating step and the copper-, nickel-, orsolder-plating step during multilayer plating is arbitrary.

The chemically amplified positive-working photosensitive resincomposition according to the present invention can also be usedfavorably as a plating resist during production of magnetic heads or thelike.

As described above, the chemically amplified positive-workingphotosensitive resin composition according to the present invention isfirst applied onto a base material such as a support plate having asneeded an electrically conductive layer formed thereon made of aconductive material such as aluminium, copper, silver, gold, palladium,or an alloy of two or more of these metals; and the resulting resinlayer is then prebaked and converted, for example, into a thick orultra-thick photoresist layer. The base materials include, in additionto the silicone substrate described above, substrates of titaniumnitride (TiN), nickel, and permalloy (alloy of iron, nickel, andothers); and substrates of soda-lime glass, quartz glass, siliconcarbide, titanium carbide, zirconium carbide, boron nitride, aluminiumnitride, silicon nitride, silicone, germanium, gallium-arsenic, andgallium-phosphorus. The photoresist layer is then pattern-exposed tolight through a mask, developed with an alkaline developing solution,and then subjected as needed to rinsing, post-exposure baking (PEB), orthe like. A thick or ultra-thick positive-working resist pattern higherin resolution and favorable in shape is formed in this manner, and isused especially favorably as a thick or ultra-thick plating resist usedin forming magnetic poles on magnetic heads, bumps, and others. Thechemically amplified positive-working photosensitive resin compositionaccording to the present invention can positively be used in the fieldswherein conventional positive-working photosensitive resin compositionshave been used, for example, as a plating resist for circuit boards andothers. In addition, the positive-working photosensitive resincomposition according to the present invention has many advantagesincluding high sensitivity, higher film retention ratio afterdevelopment, and no scum generation.

Any one of the methods used conventionally in applying photosensitiveresin compositions such as spin coating method, roll coating method,land coating method, spray coating method, flow and spread coatingmethod, and dip coating method may be used for forming the coating filmof the photosensitive resin composition according to the presentinvention.

Alternatively, the coating film may be formed if needed, for example, byscreen-printing. Examples of the radiation used in exposure includeultraviolet rays such as g-line and i-line, far ultraviolet rays such asKrF and ArF excimer lasers, X-rays, and electron beams. In addition, anyone of the methods used conventionally in developing photoresists suchas paddle developing method, dip developing method, and vibratory dipdeveloping method may be used for developing the photosensitive resincomposition according to the present invention. Examples of thedevelopers include inorganic alkali compounds such as sodium hydroxide,potassium hydroxide, sodium carbonate, and sodium silicate; ammonia;organic amines such as ethylamine, propylamine, diethyl amine,diethylaminoethanol, and triethylamine; and quaternary amines such astetramethylammonium hydroxide.

The optimal processing conditions including light-exposure condition forprocessing the chemically amplified positive-working photosensitiveresin composition according to the present invention may vary accordingto the thickness of photoresist, exposure light source, developer used,and others. But, when an ultra-thick film photoresist having a thicknessof 20 μm or more is exposed to light for example by using an HBO1000W/Dmercury lamp manufactured by Mitsubishi Electric Osram Ltd., which isused in Examples described below as an exposure light source, theexposure intensity is usually approximately 100 to 500 mJ/cm²·sec; andthe developing time is approximately 60 to 900 seconds when a commonaqueous organic or inorganic alkaline solution is used as the developerand the film is developed by the dip or paddle developing method.

In addition, the chemically amplified positive-working photosensitiveresin composition according to the present invention may also be used asa so-called dry film, which is prepared by applying a photosensitiveresin composition not directly on the substrate but on a removableplastic film, baking the resulting coated layer to form a photoresistfilm once on the temporary supporting plate of plastics film, and whichis used as adhered to a substrate to be processed such as a supportingplate. Any one of conventional plating solutions and plating methods maybe used as those used in the plating steps.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail withreference to Examples, but it should be understood that the presentinvention is not restricted by these Examples. In the followingExamples, weight-average molecular weights are values as determined bystyrene standards.

EXAMPLE 1

One hundred parts by weight of a novolak resin having a weight-averagemolecular weight of 7,000 (m-cresol: 40%, p-cresol: 60%), 15 parts byweight of a ternary copolymer of methacrylic acid, methyl methacrylate,and n-butyl acrylate (molar ratio: 20/50/30) having a weight-averagemolecular weight of 30,000, 30 parts by weight of a polymer having aweight-average molecular weight of 1,000 prepared by polycondensation oftriethylene glycol and 2-ethylbutane-1,1-diol, and 0.6 part by weight of2-[2-(5-methylfuran-2-yl)-ethenyl]-4,6-bis-(tri-chloromethyl)-s-triazineas an acid generator were dissolved in 200 parts by weight of propyleneglycol monomethylether acetate. The solution was stirred and thenfiltered through a 1.2-μm filter to give a photosensitive resincomposition according to the present invention. The composition was spincoated onto a 6-inch silicon wafer and baked at 120° C. for 5 minutes ona hot plate to give a resist film having a thickness of 25 μm. Theresist film was exposed to light through a test pattern containing holepatterns having a variety of line widths (hole diameters: from 5 to 50μm; wall widths: from 5 to 50 μm) for 10 seconds (250 mJ/cm²) by usingan HBO1000W/D mercury lamp manufactured by Mitsubishi Electric OsramLtd. in an exposure machine, MA-200/ML manufactured by Suss MicroTecK.K. and developed with a solution of AZ 303N manufactured by ClariantJapan K.K. 9 times diluted with distilled water at 23° C. for 480seconds to give a good resist pattern. In addition, the illuminance ofthe HBO1000W/D mercury lamp at 405 nm is 25 mJ/cm²·sec and AZ 303N is a4.8 wt % aqueous KOH solution. The shape of the resist pattern wasdetermined by observing a hole resist pattern having a hole diameter anda wall width respectively of 20 μm and 20 μm.

EXAMPLE 2

The same procedure as in Example 1 was carried out except for using5-methylsulfonyloxyimino-5H-thiophen-2-ylidene-2-methylphenylacetonitrileas the acid generator instead of the triazine-based acid generator, andresults in Table 1 were obtained.

EXAMPLE 3

The same procedure as in Example 1 was carried out except for using aquaternary copolymer of methacrylic acid, methyl methacrylate, n-butylacrylate, and styrene (molar ratio: 20/50/15/15) having a weight-averagemolecular weight of 30,000 instead of the ternary copolymer ofmethacrylic acid, methyl methacrylate, and n-butyl acrylate, and resultsin Table 1 were obtained.

EXAMPLE 4

The same procedure as in Example 1 was carried out except for using aternary copolymer of hydroxyethyl methacrylate, methyl methacrylate, andn-butyl acrylate (molar ratio: 20/50/30) having a weight-averagemolecular weight of 30,000 instead of the ternary copolymer ofmethacrylic acid, methyl methacrylate, and n-butyl acrylate, and resultsin Table 1 were obtained.

EXAMPLE 5

The same procedure as in Example 4 was carried out except for using 15parts by weight of the ternary copolymer (molar ratio: ditto) having aweight-average molecular weight of 80,000 as the ternary copolymer ofhydroxyethyl methacrylate, methyl methacrylate, and n-butyl acrylate,and results in Table 1 were obtained.

COMPARATIVE EXAMPLE 1

The same procedure as in Example 1 was carried out except for using aphotosensitive resin composition prepared by dissolving 100 parts byweight of a novolak resin having a weight-average molecular weight of7,000 (same as that in Example 1) and 10 parts by weight of1,2-naphthoquinone-(2)-diazide-4-sulfonate of2,3,4-tri-hydroxy-4-benzophenone in 200 parts by weight of propyleneglycol monomethylether acetate, and results in Table 1 were obtained.

COMPARATIVE EXAMPLE 2

The same procedure as in Comparative Example 1 was carried out exceptfor exposing for 40 seconds instead of for 10 seconds, and results inTable 1 were obtained.

COMPARATIVE EXAMPLE 3

The same procedure as in Comparative Example 2 was carried out exceptfor using a solution of AZ303N 5 times diluted with distilled water asthe developing solution instead of that 9 times diluted, and results inTable 1 were obtained.

TABLE 1 Film Film retention thickness Pattern ratio (%) (μm) shapeDescription Example 1 >98 25 Good Rectangular Example 2 >98 25 GoodRectangular Example 3 >98 25 Good Rectangular Example 4 >98 25 GoodRectangular Example 5 >98 25 Good Rectangular Comparative >98 25 NoExample 1 resolution Comparative >98 25 No Example 2 resolutionComparative >95 25 Unfavorable Mortar-shaped Example 3

EXAMPLE 6

The same procedure as in Example 1 was carried out except for giving aresist film of 100 μm in thickness prepared by baking at 130° C. for 5minutes on a hot plate instead of the resist film of 25 μm in thicknessprepared by baking at 120° C. for 5 minutes on a hot plate, and resultsin Table 2 were obtained.

EXAMPLE 7

The same procedure as in Example 6 was carried out except for using5-methylsulfonyloxyimino-5H-thiophen-2-ylidene-2-methylphenylacetonitrile as the acid generator instead of2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis-(trichloro-methyl)-s-triazine,and results in Table 2 were obtained.

COMPARATIVE EXAMPLE 4

The same procedure as in Example 6 was carried out except for using aphotosensitive resin composition prepared by dissolving 100 parts byweight of a novolak resin having a weight-average molecular weight of7,000 (same as that in Example 6) and 10 parts by weight of1,2-naphthoquinone-(2)-diazide-4-sulfonate of2,3,4-trihydroxy-4-benzophenone in 200 parts by weight of propyleneglycol monomethylether acetate, and results in Table 2 were obtained.

TABLE 2 Film Film retention thickness Pattern ratio (%) (μm) shapeDescription Example 6 >98 100 Good Rectangular (Slightly barrel-shaped)Example 7 >98 100 Good Rectangular (Slightly barrel-shaped)Comparative >95 100 No Example 4 resolution

EXAMPLE 8

One hundred parts by weight of a novolak resin having a weight-averagemolecular weight of 7,000 (m-cresol: 40%, p-cresol: 60%), 15 parts byweight of a ternary copolymer of hydroxyethyl methacrylate, methylmethacrylate, and n-butyl acrylate (molar ratio: 20/50/30) having aweight-average molecular weight of 32,000, 24 parts by weight of apolymer having a weight-average molecular weight of 1,000 prepared bypolycondensation of triethylene glycol and 2-ethylbutane-1,1-diol, and0.4 part by weight of N-(trifluoromethylsulfonyloxy)-1,8-naphthalimideas an acid generator were dissolved in 200 parts by weight of propyleneglycol monomethylether acetate. The solution was stirred and thenfiltered through a 1.2-μm filter to give a photosensitive resincomposition according to the present invention. The composition was spincoated onto a 6-inch silicon wafer having titanium and gold layersrespectively having thicknesses of 500 and 2,000 angstroms and baked at120° C. for 5 minutes on a hot plate to give a resist film of 25 μm inthickness. The resulting resist film was exposed to light through a testpattern containing hole patterns having a variety of line widths (holediameters: from 5 to 50 μm; wall widths: from 5 to 50 μm) for 10 seconds(250 mJ/cm²) by using the HBO1000W/D mercury lamp manufactured byMitsubishi Electric Osram Ltd. in the exposure machine, MA-200/MLmanufactured by Suss MicroTec K.K. and developed with a solution of AZ303N manufactured by Clariant (Japan) K.K. 7-times diluted withdistilled water at 23° C. for 210 seconds to give a good resist pattern.In addition, the illuminance of the HBO1000W/D mercury lamp at 405 nm is25 mJ/cm²·sec. The shape of the resist pattern was determined byobserving the shape of a hole resist pattern having a hole diameter anda wall width respectively of 20 μm and 20 μm. The wafer thus obtainedwas electroplated at 42° C. for 60 minutes under the condition of acurrent of 0.4 A/dm² by using a TEMPER EX401 gold plating solutionmanufactured by Electroplating Engineers of Japan Ltd. After plating,the resulting resist pattern was separated by processing with AZ Remover700 manufactured by Clariant (Japan) K.K. at 23° C. for 180 seconds togive a good gold-plated pattern. Plating shape was determined byobserving a plating shape of a hole pattern having a hole diameter and awall width respectively of 20 μm and 20 μm, and results in Table 3 wereobtained.

EXAMPLE 9

The same procedure as in Example 8 was carried out except for using2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis-(tri-chloroethyl)-s-triazineinstead of N-(trifluoromethyl-sulfonyloxy)-1,8-naphthalimide used as theacid generator in Example 8, and results in Table 3 were obtained.

EXAMPLE 10

The same procedure as in Example 8 was carried out except for using5-methylsulfonyloxyimino-5H-thiophen-2-ylidene-methylphenyl acetonitrileinstead of N-(trifluoromethyl-sulfonyloxy)-1,8-naphthalimide used as theacid generator in Example 8, and results in Table 3 were obtained.

EXAMPLE 11

The same procedure as in Example 8 was carried out except for using aquaternary copolymer of hydroxyethyl methacrylate, methyl methacrylate,n-butyl acrylate, and styrene (molar ratio: 20/50/15/15) having aweight-average molecular weight of 30,000 instead of the ternarycopolymer of hydroxy methacrylate, methyl methacrylate, and n-butylacrylate, and results in Table 3 were obtained.

EXAMPLE 12

The same procedure as in Example 8 was carried out except for using aMICROFAB Au660 gold plating solution manufactured by ElectroplatingEngineers of Japan Ltd. at 60° C. for 40 minutes under the condition ofa current of 0.8 A/dm² instead of using a TEMPER EX401 gold platingsolution manufactured by Electroplating Engineers of Japan Ltd. at 42°C. for 60 minutes under the condition of a current of 0.4 A/dm², andresults in Table 3 were obtained.

COMPARATIVE EXAMPLE 6

The same procedure as in Example 8 was carried out except for using aphotosensitive resin composition prepared by dissolving 100 parts byweight of a novolak resin having a weight-average molecular weight of7,000 (same as that in Example 8) and 10 parts by weight of1,2-naphthoquinone-(2)-diazide-4-sulfonate of2,3,4-trihydroxy-4-benzophenone in 200 parts by weight of propyleneglycol monomethylether acetate, and results in Table 3 were obtained.

COMPARATIVE EXAMPLE 7

The same procedure as in Comparative Example 6 was carried out exceptfor exposing to light through the test pattern for 40 seconds instead of10 seconds in the exposure machine, MA-200/ML manufactured by SussMicroTec K.K., and results in Table 3 were obtained.

COMPARATIVE EXAMPLE 8

The same procedure as in Comparative Example 7 was carried out exceptfor using the solution of AZ 303N manufactured by Clariant (Japan) K.K.8-times diluted with distilled water instead of that 5-times dilutedwith distilled water, and results in Table 3 were obtained.

TABLE 3 Film retention Pattern Plating Crack, smudge, ratio (%)Sensitivity shape shape and others * Description Example 8 >98 250mJ/cm² Good Good Naught Rectangular Example 9 >98 250 mJ/cm² Good GoodNaught Rectangular Example 10 >98 250 mJ/cm² Good Good NaughtRectangular Example 11 >98 250 mJ/cm² Good Good Naught RectangularExample 12 >98 250 mJ/cm² Good Good Naught Rectangular Comparative >98No opening No opening — Example 6 Comparative >98 No opening No opening— Example 7 Comparative >95 1,000 mJ/cm²   Good Barrel- Naught Mortar-Example 8 shaped shaped * Presence of cracks, smudges, and others wasexamined by observing the sectional form using the scanning electronmicroscope (SEM).

EXAMPLE 13

The same procedure as in Example 1 was carried out except for giving aresist film of 65 μm in thickness prepared by baking at 130° C. for 5minutes on a hot plate instead of giving the resist film of 25 μm inthickness prepared by baking at 120° C. for 5 minutes on a hot plate,and results in Table 4 were obtained.

EXAMPLE 14

The same procedure as in Example 13 was carried out except for using2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis-(tri-chloroethyl)-s-triazineas the acid generator instead ofN-(trifluoromethylsulfonyloxy)-1,8-naphthalimide, and results in Table 4were obtained.

COMPARATIVE EXAMPLE 9

The same procedure as in Example 13 was carried out except for using aphotosensitive resin composition prepared by dissolving 100 parts byweight of a novolak resin having a weight-average molecular weight of7,000 and 10 parts by weight of1,2-naphthoquinone-(2)-diazide-4-sulfonate of2,3,4-trihydroxy-4-benzophenone in propylene glycol monomethyletheracetate, and the result in Table 4 was obtained.

TABLE 4 Film retention ratio (%) Sensitivity Pattern shape DescriptionExample 13 >98 250 mJ/cm² Good Rectangular Example 14 >98 250 mJ/cm²Good Rectangular (Slightly barrel-shaped) Comparative >95 No opening NoOpening Example 9

The resulting resist patterns for preparing thick film patterns and forpreparing gold bumps both obtained in Examples according to the presentinvention had no scum and showed good shape of resist pattern. It isapparent from the Tables that the every chemically amplifiedpositive-working photosensitive resin composition according to thepresent invention is excellent in film retention ratio and sensitivity.

Further the results in Table 1 indicate that use of an acid generator(PAG) is effective in producing a photosensitive resin compositionhaving higher-sensitivity and higher-resolution than the photosensitiveresin composition produced by the use of the photosensitive agenthitherto commonly used, 1,2-naphthoquinone-(2)-diazide-4-sulfonate of2,3,4-trihydroxy-4-benzophenone. It seems to be because, in contrast tothe conventional photosensitive agent, which absorbs the light ofexposure wavelength and thus practically loses its photosensitivity inthe deeper layer of a thick film due to absorption at the upper layer,the chemical amplification system in which a PAG is used demands a smallamount of light-absorbing acid generator and thus allows patterning evenin lithography employing thick films and consequently production ofresist patterns good in shape. In addition, the results in Table 2indicate that it is extremely difficult to perform patterning by using acomposition containing a PAG when a thicker film of 100 μm or more inthickness is exposed and developed. It seems to be because the PAGabsorbs the light of exposure wavelength and the exposed light becomesmore inactivated at the bottom layer closer to the substrate, resultingin suppression of the reaction of the photosensitive agent andinhibition of the film becoming more alkali soluble. The phenomenon canbe observed in films having a thickness of more than 40 μm.

EVALUATION OF HEAT RESISTANCE

The heat resistance of the resist patterns obtained by the chemicallyamplified positive-working photosensitive resin compositions accordingto the present invention was further evaluated for heat resistance.

EXAMPLE 15

The resist pattern obtained in Example 1 was heat-treated at 90° C. forone minute on a hot plate, and the shapes of the resist pattern beforeand after heat-treatment were compared. The patterns were bothrectangular and not particularly different from each other.

COMPARATIVE EXAMPLE 10

The same procedure as in Example 1 was carried out except for preparinga photosensitive resin composition not using the ternary copolymer ofmethacrylic acid, methyl methacrylate, and n-butyl acrylate having aweight-average molecular weight of 30,000 to give a resist pattern. Thefilm retention ratio of the resulting resist pattern was 98% or more,and the pattern shape was rectangular and good. The resist pattern thusobtained was heat-treated in the same manner as in Example 15, resultingin a drooping of the pattern.

The results in Example 15 and Comparative Example 10 indicate that thephotosensitive resin composition according to the present invention isexcellent in heat resistance.

ADVANTAGEOUS EFFECT OF THE INVENTION

As described above, the present invention practically allows productionof resist patterns excellent both in resolution and sensitivity having athickness of 5 μm or more for a thick film or an ultra-thick film forforming a gold-bump, and provides a chemically amplifiedpositive-working photosensitive resin composition that is excellent incoating property, heat resistance and uniformity in the line width ofresist pattern and allows production of good patterns.

1. A chemically amplified positive-working photosensitive resincomposition, comprising (A) an alkali soluble novolak resin, (B) analkali soluble acrylic resin, (C) an acetal compound, and (D) an acidgenerator further where the weight ratio of the components(A):(B):(C):(D) is 100:(2 to 200):(1 to 50):(0.05 to 10), further wherethe acrylic resin contains a structural unit derived from hydroxyalkylmethacrylate and a structural unit derived from alkyl methacrylate, andoptionally a structural unit derived from styrene.
 2. The chemicallyamplified positive-working photosensitive resin composition according toclaim 1, wherein the acetal compound has a structural unit representedby the following general formula (I):

wherein R represents a saturated alkyl group having 1 to 20carbon-atoms; and n is an integer of 1 to
 10. 3. A coated substratecomprising a coating of the chemically amplified positive-workingphotosensitive resin composition of claim 1, wherein the coating has afilm thickness of 5 μm or more.
 4. A process comprising imaging thechemically amplified positive-working photosensitive resin compositionof claim 1 and followed by forming a cyan or non cyan electrolytic goldplating layer.
 5. The process of claim 4 wherein plating layer is amultilayer.
 6. The process of claim 5, where the multilayer comprises agold layer and at least one additional layer selected from copper,nickel and solder.
 7. A process comprising imaging the chemicallyamplified positive-working photosensitive resin composition of claim 1and followed by forming a plating layer selected from copper, nickel andsolder.
 8. The process of claim 7, wherein the plating layer is amultilayer.
 9. The process of claim 8, where the multilayer comprises atleast one layer selected from copper, nickel and solder, and at leastone additional layer comprising gold.